Drive Unit For Shifting A Torque Balance

ABSTRACT

A drive unit utilizing a double planetary differential and an overdriven gear to shift torque between output shafts. The drive unit includes a motor, a differential caging housing a planetary differential and in driving engagement with two output shafts, a planetary carrier, a first gear, a second gear, and two variably engageable clutches. The planetary carrier supports the planetary differential and is drivingly engaged with a first output shaft. The first gear is capable of being overdriven and is in driving engagement with the motor and the variably engaged clutches. The second gear is in driving engagement with the motor and the differential caging. The first clutch is disposed between the first gear and the second output shaft and the second clutch is disposed between the first gear and the planetary carrier. When the clutches are actuated, torque is shifted between the output shafts via the first gear.

RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.14/991,201 filed on Jan. 8, 2016, which is fully incorporated byreference herein.

FIELD OF THE INVENTION

The present invention relates to a drive unit utilizing a doubleplanetary differential arrangement and an overdriven gear which may bevariably engaged with two output shafts of the double planetarydifferential arrangement to shift torque between the two output shafts.

BACKGROUND OF THE INVENTION

Drive units typically comprise a motor and a reduction drive arranged toreduce the rotational movement produced by the motor. Torque istransmitted from the reduction drive to a differential assembly whichsplits the torque onto two output shafts for driving wheels.

Electric or hybrid vehicles using a drive unit have long been known.Hybrid electric vehicles typically have a structure which combines twopower sources, an electric motor and an internal combustion engine, toproduce lower emissions. Hybrid electric drive units are being developedfor use in all-wheel drive vehicles such that the electric motor and anengine can transmit power to both a front set of driven wheels and rearset of driven wheels.

In all-wheel drive hybrid electric vehicles, typically a reducing gearset reduces an output speed from an electric motor and transmits thereduced output speed to a differential gear assembly. The differentialgear assembly distributes the introduced torque to two output shafts sothat of one of the two output shafts can rotate at a different rate withrespect to one another.

It would be advantageous to develop a drive unit capable of precisetorque distribution between two output shafts and respective wheels toprovide improved stability and agility to a motor vehicle.

SUMMARY OF INVENTION

The present invention relates to a drive unit utilizing a doubleplanetary differential gear arrangement and an overdriven gear to shifttorque between two output shafts. The drive unit includes a motor, adifferential caging which houses a double planetary gear arrangement indriving engagement with two output shafts, a planetary carrier, a firstgear, a second gear and a pair of variable engaged clutches. Theplanetary carrier supports the double planetary differential geararrangement and is driving engagement with a first output shaft. Thefirst gear is in drivingly engaged with the motor and the variablyengaged clutches. The second gear is in driving engagement with themotor and the planetary gears of the differential gear arrangement. Thefirst gear is capable of being over driven by the motor with respect tothe second gear. The first variably engageable clutch is disposedbetween the first gear and the second output shaft and the secondvariably engageable clutch is disposed between the first gear and theplanetary carrier. When the first variable engageable clutch isactuated, an increased torque is applied to the first output shaft andwhen the second variably engageable clutch is actuated, an increasedtorque is applied to the second output shaft.

BRIEF DESCRIPTION OF THE DRAWINGS

The above, as well as other advantages of the present invention, willbecome readily apparent to those skilled in the art from the followingdetailed description when considered in the light of the accompanyingdrawings in which:

FIG. 1 is a schematic view of the drive unit assembly in accordance witha preferred embodiment of the invention; and

FIG. 2 is a schematic view of the drive unit assembly in accordance withanother preferred embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

It is to be understood that the invention may assume various alternativeorientations and step sequences, except where expressly specified to thecontrary. It is also to be understood that the specific devices andprocesses illustrated in the attached drawings, and described in thefollowing specification are simply exemplary embodiments of theinventive concepts defined in the appended claims. Hence, specificdimensions, directions or other physical characteristics relating to theembodiments disclosed are not to be considered as limiting, unless theclaims expressly state otherwise.

Referring now to FIG. 1 of the drawings, one preferred embodiment of theelectric drive unit assembly 10 is provided.

As shown in FIG. 1, a motor 11 is connected to a first housing member 12and an output shaft 13. The motor 11 can be any type of motor includingan electric or hydraulic motor. The first housing member 12 extendsaxially from the motor 11 and is radially outward compared to outputshaft 13. Output shaft 13 extends axially from the motor and is radiallyinward from the first housing member 12.

Output shaft 13 is drivingly engaged to a reducing gear set 14. Thereducing gear set 14 comprises a first reducing gear 14 a and a secondreducing gear 14 b. The first reducing gear 14 a is positioned radiallyinward from output shaft 13. The first reducing gear 14 a is drivinglyengaged with output shaft 13.

The second reducing gear 14 b is connected to the first reducing gear 14a by a shaft 14 c which extends axially from the first reducing gear 14a. A driving gear of the second reducing gear 14 b is capable of beingengaged with a first clutching device 15.

The first clutching device 15 is positioned radially outward from thesecond reducing gear 14 b and is supported by a second housing member16. The first clutching device 15 can be actuated by any means,particularly, electro-mechanical, hydraulic or electro-magnetic means.As shown in FIG. 1 the first clutching device is a dog clutch, but canbe any type of clutching device.

The first clutching device 15 is capable of selectively coupling thesecond reducing gear 14 b and a pinion gear 17. Pinion gear 17 has twopinions 17 a, 17 b connected by an axially extending shaft 17 c. Thepinion gear 17 is rotatable around the shaft 14 c of the reducing gearset. Pinions 17 a, 17 b have teeth formed thereon. Pinion 17 a iscapable of engaging the first clutching device 15. Pinion 17 b isdrivingly engaged with a set of ring gears 18, 19. Pinion 17 b and ringgears 18, 19 have a common center distance.

The ring gears 18, 19 are positioned radially inward from pinion gear17. The ring gears 18, 19 have teeth disposed thereon. The first ringgear 18 has fewer gear teeth than the second ring gear 19 allowing thefirst ring gear 18 to be driven faster that the second ring gear.Therefore, the first ring gear 18 is overdriven with respect to thesecond ring gear 19.

In one preferred embodiment, the pinion gear 17 has 17 teeth, the firstring gear 18 has 50 teeth and the second gear 19 has 51 teeth. In otherembodiments, the number of teeth on each gear can be selected to give anover speed of about 2 to about 4.5 percent of the first ring gear 18with respect to the second ring gear 19.

The first housing member 12 is disposed radially outward from ring gear19 and the second housing member 16 is disposed radially outward fromring gear 18. A third housing member 20 is disposed between gears 18,19. As shown in FIG. 1, a portion of the third housing member 20 islocated between the first housing member 12 and the second housingmember 16, fixing the axial position of the third housing member 20without requiring additional means of retention including retentionbolts. The shape of the third housing member 20, as shown in FIG. 1,prevents rotation of the housing. In other embodiments, other means canbe used to prevent rotation, including dowels.

The first ring gear 18 is connected to a radial shaft 21. Radial shaft21 extends radially inward from first ring gear 18 and has a firstclutch hub 22 extending axially outward from the other end thereof. Theclutch hub 22 has one set of clutch plates 23 extending radially outwardthereon and a second set of clutch plates 24 extending radially inwardthereon.

A second clutch hub 25, parallel to clutch hub 22 and radially outwardtherefrom, has a set of clutch plates 26 extending radially inwardthereon. Clutch plates 23 and 26 are interleaved to form a clutch pack.The second clutch hub 25 extends axially from a radially extendingoutput shaft 27. The output shaft 27 extends radially inward from theend of second clutch hub 25 towards a rotational axis Z. Clutch plates23, 26, clutch hubs 22, 25 and shaft 27 form a first variably engageableclutch 28. Shaft 27 has a gear 27 a formed on the radially inward endwhich is drivingly engaged with a first output shaft 29. Output shaft 29is an axle half shaft of a motor vehicle. When the first variablyengageable clutch 28 is engaged, torque is transferred from the motorthrough the first ring gear 18 and shaft 27 to output shaft 29.

A third clutch hub 30, parallel to clutch hub 22 and radially inwardtherefrom, has a set of clutch plates 31 extending radially outwardthereon. Clutch plates 24, 31 are interleaved to form a clutch pack.Clutch plates 24, 31, clutch hubs 22, 30 and shaft 27 form a secondvariably engageable clutch 32.

The third clutch hub 30 is connected to the end of a planetary gearcarrier 33. The planetary gear carrier 33 extends axially from the thirdclutch hub 30 toward a planetary differential gear arrangement 39 and isrotatable around the rotational axis Z.

The planetary gear carrier 33 provides support for a set of planetarygears 35, 36 and is drivingly connected to a second output shaft 34. Theplanetary gear carrier 33 has two parallel axial sections 33 a, 33 bwhich are connect to parallel radial sections 33 c, 33 d. Sections 33 a,33 b support planetary gear sets 35, 36. Section 33 a is radiallyoutward from section 33 b and supports a planetary gear set 35. Section33 b is radially inward from 33 a and supports planetary gear set 36.

When the second variably engageable clutch 32 is engaged, torque istransferred from motor through the first ring gear 18 and planetary gearcarrier 33 to output shaft 34.

The variably engageable clutches 28, 32 can be actuated by separateactuators or can be actuated by a single actuator configured to operateonly one clutch at any time. The variably engageable clutches 28, 32 canbe actuated by any mechanical means, i.e. motor, actuator gears, ballramp actuator, or by hydraulic or electro-magnetic means.

The second ring gear 19 is attached via a shaft 37 to a differentialcaging 38. The shaft 37 extends radially inward from the second ringgear 19 and radially outward from differential caging 38. Differentialcaging 38 is bell-shaped and houses the planetary differential geararrangement 39. Differential caging 38 includes an axial section 38 a.Section 38 a of the differential caging has a gear 40 extending radiallyinward thereon. Gear 40 is drivingly engaged with the first planetarygear set 35 which is drivingly engaged to the second planetary gear set36. The first planetary gear set 35 is radially outward from the secondplanetary gear set 36. The second planetary gear set 36 is drivinglyengaged to a sun gear 41 which is connected to output shaft 29.

A first bearing 42 is disposed between the radial shaft 21 and housingmember 20 and supports gear 18. A second bearing 43 is disposed betweendifferential caging 38 and housing member 20 and supports the planetarydifferential gear arrangement 39. The second bearing 43 is adjacent tothe first bearing 42. Both bearings 42, 43 are supported by the housingmember 20.

The output shafts 29, 34 are axle half shafts connected to right andleft wheels (not shown) of a motor vehicle respectively. The drive unitcan be employed as rear drive unit or a front drive unit. The outputshafts 29, 34 rotate in the same direction and same speed while allowingdifferential action to occur if needed.

During normal operation, the speed difference that occurs across thevariably engageable clutches 28, 32 is small and allows for a low clutchdraft, a reduced clutch clearance, and high actuation speeds.

The first clutching device 15 when engaged couples the reducing gear set14 to pinion gear 17. When the first clutching device 15 is disengaged,the motor 11 and the reducing gear set 14 is disconnected from outputshafts 29, 34 and allows the output shafts 29, 34 to idle. When used asa secondary all-wheel driveline, output shafts 29, 34 rotate at wheelspeed allowing the motor to become stationary, reducing drag andimproving fuel economy. Additionally, the first clutching device 15 canbe disengaged to limit the maximum motor speed under high drivingspeeds.

By controlling the variably engageable clutches 28, 32, the torque canforceably be transferred between output shafts 29, 34. When additionaltorque is needed at output shaft 29, the first variably engageableclutch 28 can be engaged allowing a second power path to form to outputshaft 29 through the first ring gear 18. When additional torque isneeded at output shaft 34, the second variably engageable clutch 32 canbe engaged allowing a second power path to form to output shaft 34through the first ring gear 18 and planetary carrier 33.

If the first clutching device 15 is disengaged and the motor and ringgears are disconnected, variably engageable clutches 28, 32 can still becontrolled to balance torque to flow to output shafts 29, 34.

FIG. 2 illustrates an electric drive unit according to anotherembodiment of the invention. The embodiment shown in FIG. 2 includessimilar components to the electric drive unit illustrated in FIG. 1.Similar structural features of the electric drive unit 110 include thesame reference numeral and a prime (′) symbol, with the exception of thefeatures described below.

The embodiment of the electric drive unit 110 as shown in FIG. 2 issimilar to the electric drive unit 10, with the exception of the use ofa pinion gear 117 having three pinion 117 a, 117 b, 117 c, whichoperates similar to the pinion gear 17 illustrated in FIG. 1. The piniongear 117 has three pinions 117 a, 117 b, 117 c connected to an axiallyextending shaft 117 d. Pinion 117 a is capable of engaging the firstclutching device 15′. Pinion 117 b is drivingly engaged with ring gear18′ and pinion 117 c is drivingly engaged with ring gear 19′. Pinions117 a, 117 b, 117 c have teeth formed thereon. The number of teeth onpinion 117 b and on pinion 117 c are different from one another allowingfor alternative speed ratios between the first 18′ and second 19′ gears.

In accordance with the provisions of the patent statutes, the presentinvention has been described in what is considered to represent itspreferred embodiments. However, it should be noted that the inventioncan be practiced otherwise than as specifically illustrated anddescribed without departing from its spirit or scope.

What is claimed:
 1. A drive unit for a vehicle, comprising: a motor; a first gear in driving engagement with the motor; a second gear in driving engagement with the motor; a differential caging having a third gear in driving engagement with a planetary differential gear arrangement disposed therein, wherein the planetary differential gear arrangement is in driving engagement with a first output shaft; a planetary gear carrier configured to support at least a portion of the planetary differential gear arrangement, wherein the planetary gear carrier is in driving engagement with a second output shaft; a pinion gear disposed between the motor and at least one of the first and second gears, wherein the pinion gear includes a first pinion and a second pinion, and wherein the second pinion is in driving engagement with at least one of the first and second gears; a first variably engageable clutch disposed between the first gear and the first output shaft to selectively transfer torque from the first gear to the first output shaft; and a second variably engageable clutch disposed between the first gear and the planetary gear carrier to selectively transfer torque from the first gear to the second output shaft via the planetary gear carrier.
 2. The drive unit of claim 1, wherein the first and second gears have gear teeth disposed thereon, and wherein a number of the gear teeth on the first gear is less than a number of the gear teeth on the second gear.
 3. The drive unit of claim 1, further comprising a reducing gear set positioned between the motor and the first and second gears, wherein the reducing gear set is in driving engagement with the motor and the first and second gears.
 4. The drive unit of claim 1, wherein the second gear is in driving engagement with the third gear of the differential caging.
 5. The drive unit of claim 1, wherein the planetary differential gear arrangement includes a first planetary gear set and a second planetary gear set.
 6. The drive unit of claim 5, wherein the third gear is in driving engagement with the first planetary gear set.
 7. The drive unit of claim 1, further comprising a clutching device positioned between the motor and the first and second gears to selectively connect and disconnect the motor from the first and second gears.
 8. The drive unit of claim 7, wherein the clutching device is configured to selectively engage the first pinion of the pinion gear.
 9. The drive unit of claim 1, wherein the pinion gear further includes a third pinion.
 10. The drive unit of claim 9, wherein the second pinion of the pinion gear is in driving engagement with the first gear and the third pinion of the pinion gear is in driving engagement with second gear.
 11. A drive unit for a vehicle, comprising: a motor; a first gear in driving engagement with the motor; a second gear in driving engagement with the motor; a differential caging having a planetary differential gear arrangement disposed therein, wherein the planetary differential gear arrangement is in driving engagement with a first output shaft; a planetary gear carrier configured to support at least a portion of the planetary differential gear arrangement, wherein the planetary gear carrier is in driving engagement with a second output shaft; a pinion gear disposed between the motor and at least one of the first and second gears, the pinion gear including a first pinion, a second pinion, and a third pinion, wherein the second pinion is in driving engagement with the first gear and the third pinion is in driving engagement with the second gear; a first variably engageable clutch disposed between the first gear and the first output shaft to selectively transfer torque from the first gear to the first output shaft; and a second variably engageable clutch disposed between the first gear and the planetary gear carrier to selectively transfer torque from the first gear to the second output shaft via the planetary gear carrier.
 12. The drive unit of claim 11, further comprising a reducing gear set positioned between the motor and the first and second gears, wherein the reducing gear set is in driving engagement with the motor and the first and second gears.
 13. The drive unit of claim 11, wherein the differential caging further includes a third gear disposed therein.
 14. The drive unit of claim 13, wherein the second gear is in driving engagement with the third gear of the differential caging.
 15. The drive unit of claim 13, wherein the third gear is in driving engagement with the planetary differential gear arrangement.
 16. The drive unit of claim 11, further comprising a clutching device positioned between the motor and the first and second gears to selectively connect and disconnect the motor from the first and second gears.
 17. The drive unit of claim 16, wherein the clutching device is configured to selectively engage the first pinion of the pinion gear.
 18. A method for selectively shifting torque between output shafts of a vehicle, comprising: providing a motor; providing a first gear in driving engagement with the motor; providing a second gear in driving engagement with the motor; providing a differential caging having a third gear in driving engagement with a planetary differential gear arrangement disposed therein, wherein the planetary differential gear arrangement is in driving engagement with a first output shaft; providing a planetary gear carrier configured to support at least a portion of the planetary differential gear arrangement, wherein the planetary gear carrier is in driving engagement with a second output shaft; providing a pinion gear disposed between the motor and at least one of the first and second gears, wherein the pinion gear includes a first pinion and a second pinion, and wherein the second pinion is in driving engagement with at least one of the first and second gears; providing a first variably engageable clutch disposed between the first gear and the first output shaft; providing a second variably engageable clutch disposed between the first gear and the planetary gear carrier; selectively shifting torque from the motor to the first output shaft by selectively engaging the first variably engageable clutch; and selectively shifting torque from the motor to the second output shaft via the planetary gear carrier by selectively engaging the second variably engageable clutch.
 19. The method of claim 18, wherein the pinion gear further includes a third pinion.
 20. The method of claim 19, wherein the second pinion of the pinion gear is in driving engagement with the first gear and the third pinion of the pinion gear is in driving engagement with second gear. 